Building the 1/4-Scale 5 HP Red Wing: Part V


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Editor's note: This is the fifth and final installment on building the Red Wing engine.

Hello again! This is the last part of the Red Wing series. I have received several e-mails and even a letter commenting on this series. It's wonderful that something published in a magazine is actually appreciated by the readers. Thanks for reading!

Everything was finished in the last article except for the mixer and how to hook up the wires. We are going to cover both in this article! To finish off the mechanical components, lets hit the mixer first.

Step 16: Constructing the Mixer

The mixer was the most difficult part of the engine according to several of our readers. I still think the head was the toughest. However, the mixer is tricky if you don't pay close attention to the blueprints. Let me cover the highlights of the mixer and you can decide for yourself.

The mixer starts out as two brass castings (Photo 1). The top portion I will refer to as the bushing and the main casting. There is a trick to getting all of this aligned perfectly.

The bushing is the first part I worked with. I used a 1-inch belt sander to remove the rough stuff from the casting. Then I chucked it on the lathe. With the head of the bushing in the chuck, I was able to turn the stub to a perfect 1/2-inch.

Next, I drilled a hole in its center so I could thread it for 8-inch pipe thread. This would be the connection between the mixer and the head. It would also allow me to chuck the bushing in the lathe's tail stock for the threading process.

While the bushing was still in the lathe, I chucked an 8-inch pipe thread tap in the tail stock and manually turned the lathe while feeding the tap. This allowed me to get a perfectly aligned thread before I started the next process.

To thread the stub, I put the die into the chuck of the lathe. Next, I put the bushing on an 8-inch pipe and chucked the pipe into the tail stock. It was very easy to manually turn the lathe while pushing the bushing into the die from the tail stock holder. So far this has given me a perfectly-aligned pipe thread and 1/2-inch thread for the bushing-to-mixer interface (Photo 2).

Now for the hard part: the mixer body itself. There is a stub on the end of the mixer casting (see arrow in photo 1) so you can chuck it into the lathe. This stub will get cut off later, so do everything you can while the mixer casting is chucked in this position.

Before we go any further, I want to show you the finished mixer (Photo 3). I think it will help some of you understand how one part of the mixer relates to the other parts.

The top part of the casting has to be turned and faced just to clean it up a little. Next, an 8-inch hole is drilled from the top of the mixer casting, into the first chamber, through the second chamber and until it is well within the stem that is held by the chuck. The portion of the hole that is in the stem will act as the valve guide.

The passage between the first and second chamber inside the mixer is enlarged to allow air to pass around the valve stem. The bottom of this first chamber will be the seat for the valve (Photo 4). It should be tapered at a 45 degree angle according to the prints.

If you take a look at photo 5, you will see a small hole in the valve seat. That little hole is the passage from the mixing chamber, down to the needle valve. Obviously the needle valve is what controls how much fuel is sucked into the mixing chamber when the engine is on the intake stroke. This little passage is drilled with a tiny number 65 bit.

How does the fuel get from the fuel line over to the needle valve? This will make the sweat bead on your forehead. You must drill two small holes into the casting. The scary part is that these two holes have to intersect with each other without breaking into any of the chambers inside the casting (Photo 6). I followed the angles and directions on the blueprints and had no problems.

The valve has to be seated just like the valves in the head were. The only difference is this time we are dealing with brass-on-brass instead of steel-on-steel. The valve is held in position by a spring and keeper as can be seen in photo 3.

I have to admit that I went the easy way on one part of the mixer. The fuel line connection and needle valve are store bought. However, I still had to modify the tip of the needle valve by shortening it and changing it to a 15 degree angle. The main reason I went with store bought parts was because I was running short on time.

Step 17: Cam and Ignition Timing

With the mixer screwed into position (Photo 7), I am ready to test-fire this bad boy! That is, as soon as I set the timing and attach a few wires.

The flywheel turns clockwise when viewed from the governor side of the engine. The timing has to be set first, so start with the piston at top dead center. Now set the timing lever so it is vertical. The ignition stud should just start to make contact with the metal insert that is in the non-conductive material that turns with the timing gear (Photo 8).

The way to adjust this is to slide the whole timing assembly off the shaft, turn the timing gear and slide it back onto the shaft. Fine tuning of the ignition timing can be done with the lever. Now we can move on to the cam.

To set the cam, start turning the flywheel until you have gone 155 degrees. Sounds tough, but 180 minus 155 equals 25. Does 25 sound familiar? It should. Twenty-five degrees is the angle the bearing base on the engine frame was milled. All you have to do is set the throw of the crankshaft to the same angle as the mating surface of the bearing base and bearing caps.

Now that everything is in the correct position, adjust the cam so it is just starting to move the pushrod. Remember, the cam and timing gear turn the opposite direction of the flywheels. You will know if you set the cam on the correct side of the pushrod by turning the flywheel a little further. If it is set correctly, the pushrod will start to open the exhaust valve.

Step 18: Wiring and Firing

The only thing left is wiring. These things are so simple to wire, it almost doesn't need explaining, but I will hit on it just the same. This little engine uses a buzz coil as its ignition source. I didn't know what to expect until I saw one. It is a very simple device that would take another article to explain in detail. However, all you have to know to get your engine going is where to connect the three wires. It couldn't be simpler.

One wire goes directly from the buzz coil to the spark plug. One wire goes from the ignition stud to the buzz coil. The other connection on the buzz coil goes to the positive side of the battery. There are your three wires. One more wire is added from the engine frame to the negative side of the battery to complete the circuit.

With the needle valve turned in all the way and then backed off just a little, I gave the engine a spin and nothing happened. I did this a few more times and decided the engine needed to be broken in a little before it would start.

I disconnected the battery, then chucked a 1/2-inch drill motor to the crankshaft and gave the trigger a squeeze. I spun the engine for about two minutes. I reconnected the battery and gave the engine another spin. It fired up and ran for a good 10 or 15 seconds. A little tweaking with the needle valve and my little engine is singing that familiar tune. Hit, miss, miss, miss, hit, miss, miss, miss.

This is the most exciting project I have ever worked on. I have spent many hours teaching myself how to use a mill and a lathe. I took a box full of rough castings and turned them into a work of art! Well, there are a few rough edges on my Red Wing, but it is a work of art to me.

I am sure there are a lot of people that would love to feel the satisfaction of having built something like this for yourself. I just proved to you it can be done by anyone that has a little common sense and is willing to spend the time to make it happen. This was my first model, but I am sure it will not be my last!

Contact engine enthusiast Richard Allen Dickey at: 246 Skyview Lane, Yellville, AR 72687;
Contact the Red Wing Motor Co. at: (660) 428-2288;